ATMs (automatic teller machine) in banks and the like, or some information devices such as personal computers require a user to input a unique password. In the most common method for inputting the password, the user is asked to select or input numerals and/or characters.
Recently, a new method has been proposed. In this method the user is asked to select a certain area in an image displayed for him, and then, the information relating to that area is input as the password. This technique is explained in detail below with the help of FIG. 9. In this method, an image is displayed for the user and they are asked to select desired areas (rectangles) in the image. Information corresponding to the areas selected by the user is input as passwords. For example, if a user sequentially selects “right eye→left ear→mouth→nose” in the display image in the diagram, coordinates of these areas, i.e., “(4, 5)→(8, 5)→(5, 8)→(5, 6)”, are input as the password.
In another conventional method, many images are displayed one by one and the user is asked to select a desired area in each image. For example, the image shown in FIG. 9 is displayed one by one, and information corresponding to the area selected by the user in each image is input as the password.
These conventional methods make it easy for the user to remember the password because the user needs to simply visually remember areas of the image corresponding to his/her password.
However, the conventional methods have a problem that the password can be easily stolen by a third party, by just watching the operations performed by the user. In other words, although there is a merit that it is easy for the user to remember the password, there is a demerit that it is also easy for the third party to remember the password.
One approach to solve this problem is to increase the area in an image, or to increase the number of the images. However, there is a drawback that this increases the amount of information that the user is required to remember.
Thus, the issues those need to be solved are: how to make the password easy for the user to remember and how to make the password difficult for the third party to remember.